1. Field of the Invention
The present invention relates to temperature control systems, and more particularly to an auxiliary temperature monitoring circuit useful to detect over or under temperatures in heating or cooling environments.
2. Background Art
Temperature monitoring circuitry has become well known and an integral portion of many household appliances, such as microwave ovens, convection ovens, room heaters, dryers, and many more. Temperature control systems also find their usage in systems of cold control, such as refrigerators, freezers, air-conditioning systems, etc.
Most existing temperature control circuits are part of a master or main controller system in today's technology, usually employing a microprocessor circuit. As long as the circuit is functioning correctly, temperatures will be fed back to the microprocessor and in turn the microprocessor will turn off relays or solid state switching devices until the temperature measured by an associated sensor is acceptable. This particular type of control will not function properly if the microprocessor, the clock circuit, temperature detection circuit, or relay circuit should fail. Present safety methods typically utilize a so-called "watchdog" function wherein the main loop control circuitry must maintain the proper settings, or in turn the watchdog circuit will inhibit the operative functions.
Accordingly, it has been found most desirable to provide a separate monitoring and control system which will be able to override a master control system should the master control system or any of its portions malfunction.